Datasheet
TMC5062 DATASHEET (Rev. 1.11 / 2017-MAY-16) 70
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Parameter
Description
Range
Comment
vhighfs
&
vhighchm
These chopper configuration flags in CHOPCONF
need to be set for dcStep operation. As soon as
VDCMIN becomes exceeded, the chopper becomes
switched to fullstepping.
0 / 1
set to 1 for dcStep
TOFF
dcStep often benefits from an increased off time
value in CHOPCONF. Settings >2 should be
preferred.
2… 15
Settings 8…15 do not make
any difference to setting 8
for dcStep operation.
VDCMIN
This is the lower threshold for dcStep operation.
Below this threshold, the motor operates in
normal microstep mode. In dcStep operation, the
motor operates at minimum VDCMIN, even when
it is completely blocked. Tune together with
DC_TIME setting.
0… 2^22
0: Disable dcStep
Set to the low velocity
limit for dcStep operation.
DC_TIME
This setting controls the reference pulse width for
dcStep load measurement. It must be optimized
for robust operation with maximum motor torque.
A higher value allows higher torque and higher
velocity, a lower value allows operation down to
a lower velocity as set by VDCMIN.
Check best setting under nominal operation
conditions, and re-check under extreme operating
conditions (e.g. lowest operation supply voltage,
highest motor temperature, and highest supply
voltage, lowest motor temperature).
0… 255
Lower limit is t
BLANK
(as
defined by TBL) in clock
cycles + 1
DC_SG
This setting controls stall detection in dcStep
mode. Increase for higher sensitivity.
A stall can be used as an error condition by
issuing a hard stop for the motor. Enable sg_stop
flag for stopping the motor upon a stall event.
This way the motor will be stopped once it stalls.
0… 255
Set slightly higher than
DC_TIME/16
13.5 Measuring Actual Motor Velocity in dcStep Operation
dcStep has the ability to reduce motor velocity in case the motor becomes slower than the target
velocity due to mechanical load. VACTUAL shows the ramp generator target velocity. It is not
influenced by dcStep. Measuring dcStep velocity is possible based on the position counter XACTUAL.
Therefore take two snapshots of the position counter with a known time difference:
Example:
At 16.0 MHz clock frequency, a 0.954 second measurement delay would directly yield in the
velocity value, a 9.54 ms delay would yield in 1/100 of the actual dcStep velocity.
To grasp the time interval as precisely as possible, snapshot a timer each time the transmission of
XACTUAL from the IC starts or ends. The rising edge of NCS for SPI transmission provides the most
exact time reference.